The writing produced from the convenient ballpoint pen available in the market is not erasable by using the common eraser. Therefore, it is very inconvenient to use the conventional ballpoint pen if there is a slip of the pen which needs to be corrected or deleted. And if some special eraser, which can scrape the paper surface off, is to be used, then the paper surface will be damaged. As to the use of a chemical ink remover, such are usually toxical, and unhealthful to human beings.
It is well-known that paper is made of cellulose fibers which has capillary attraction. The ink used in the conventional ballpoint pen consists of oily dyestuffs, or oily precipitated pigments, which diffuse into the carriers, such as: mineral oils, fatty oils, or alcohols with polyethylene bases or resins with chloro-polyethylene bases; besides it also consists of polyethylene glycol which is to be used as viscosity adjusting agent.
For example, the composition of the U.S. Pat. No. 2,882,172 ballpoint pen ink is as follows:
______________________________________ Components Wt. % ______________________________________ Victoria blue oleate 56 Victoria blue phorpho-tungstic toner 27 "Crill" 5.6 2 "Carbowax" 1500 8 Polyethylene glycol 400 7 ______________________________________
The above listed components, after being thoroughly mixed, can be used as the material for making the ballpoint pen ink. However, the characteristics of this kind of ballpoint pen ink is: very quick in drying and very strong in permeability. When this kind of ink is written on paper, it is quickly absorbed by the capillary tubes within the paper sheets, and will be cured and dried very quickly. The reslt will be such that the ink can not be erased even immediately after it has been written on the paper. This is a major defect when a slip of the pen in the document has to be corrected. Besides, this kind of the ink will not smoothly and continuously be written onto the paper through the ballpoint pen, and the problem of leakage.
For this reason, the inventor studied earnestly and developed this invention of an improved formula for the ballpoint pen ink, characterized by using some high-boiling. points (188.2.degree. C. and 198.degree. C. respectively) organic compounds, such as a propylene glycol or hexylene glycol, as pigment solvent, which, under room temperature, can be maintained in a liquid state and its viscosity will not be greatly affected by a change of temperature. Therefore, no permeability defect will occur, so that the components of the ink, especially the pigment, will not be absorbed into the capillary tubes of the paper sheets and, thus, the ink can be easily erased by the common eraser.
The components of the erasable ballpoint pen ink of this invention are listed as follows:
______________________________________ Alcohol soluble pigments, about 10-20% by wt. Carrier, about 40-70% by wt. Solvent, about 15-35% by wt. Glycerol, about 3-15% by wt. ______________________________________